MESOSCALE PRECIPITATION DISCUSSION 0528
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
604 PM EDT MON SEP 28 2015
 
AREAS AFFECTED...FL PANHANDLE, SOUTHEAST AL, & SOUTHWEST GA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 282203Z - 290403Z
 
SUMMARY...A SLOWLY PROGRESSIVE BAND OF RAIN AND THUNDERSTORMS
CONTINUES ACROSS THE FL PANHANDLE AND SOUTHEAST AL.  HOURLY RAIN
RATES UP TO 3" REMAIN POSSIBLE, WHICH COULD LEAD TO FLASH
FLOODING, PARTICULARLY IN URBAN AREAS.

DISCUSSION...A LONG-LIVED RAIN BAND HAS BEEN EDGING EASTWARD AT
5-10 KTS SINCE THIS TIME YESTERDAY, WITH CONVECTIVE ELEMENTS
FOLLOWING THE 1000-500 HPA THICKNESS PATTERN AND HEAVY STRATIFORM
RAINS EXTENDING NORTHWARD.  EVERY SEVERAL HOURS, CONVECTION HEADS
A FEW COUNTIES INLAND, AND THEN RECEDES -- IT HAS BEEN CYCLICAL
AND THOUGH IT CURRENTLY APPEARS STABLE INTO AREAS NEAR AND WEST OF
VALPARAISO FL.  RECENT OBSERVATIONS INDICATE HEAVY RAINFALL
CONTINUES, WITH DESTIN FL REPORTING ~3.5" IN TWO HOURS.  DESPITE
THE HOUR OF THE DAY, CIN REMAINS ACROSS THE FL PANHANDLE/SOUTHWEST
GA AND AL DUE TO EXTENSIVE CLOUDINESS AND RAIN THROUGHOUT THE DAY.
 INFLOW AT 850 HPA REMAINS 20-30 KTS OUT OF THE EAST-SOUTHEAST,
ADVECTING IN MUCAPES FROM THE EAST OF 1000-3000 J/KG ACROSS
SOUTHEAST GA AND NORTHEAST FL.  PRECIPITABLE WATER VALUES REMAIN
BETWEEN 2.2-2.5", WHICH IS CLOSE TO 2.5 SIGMAS ABOVE THE NORM FOR
LATE SEPTEMBER.  SATELLITE TRENDS CONCERNING CLOUD TOP TEMPERATURE
CONTINUE TO PULSE IN THE AREA, WITH NEW CONVECTION ON THE
NORTHWEST PERIPHERY OF THE GULF DISTURBANCE CONTINUING TO STREAM
TOWARDS THE FL PANHANDLE COAST.  IN ADDITION TO THE GULF SYSTEM,
THERE IS A CONNECTION ALOFT TO HURRICANE MARTY WITHIN
INFRARED/WATER VAPOR SATELLITE IMAGERY.

THE MESOSCALE GUIDANCE SHOWS A DOWNTURN IN ACTIVITY SHORTLY. 
THERE IS NO INDICATION OF THIS HAPPENING PER AVAILABLE
RADAR/SATELLITE IMAGERY.  HOWEVER, THE RAP/HRRR IN PARTICULAR HAVE
BADLY INITIALIZED THE POSITION OF THE TROPICAL DISTURBANCE/GULF
GALE OFFSHORE FORT MYERS AND MOVE IT TO THE FL PANHANDLE COAST 4-6
HOURS FASTER THAN THE GLOBAL GUIDANCE, WHICH POTENTIALLY SHUTS OFF
INFLOW/UPSTREAM INSTABILITY INTO THIS BAND PREMATURELY.  AFTER
CONSULTING WITH SAB/NESDIS, CONCUR THAT HEAVY RAIN ISSUES SHOULD
PERSIST FOR ANOTHER SEVERAL HOURS.  LOW-LEVEL INFLOW IS EXPECTED
TO REMAIN STEADY DURING THE PERIOD, THOUGH MUCAPE VALUES SHOULD
BEGIN TO DECLINE AFTER SUNSET.  ONE CONCERN IS THAT THE BACK EDGE
OF CLOUDINESS/RAINFALL HAS NOT MOVED OVER THE PAST FIVE HOURS,
INDICATING THE POTENTIAL STALLING OF THE RAIN BAND.  THE CAM
GUIDANCE APPEARS BADLY PLACED AND TOO LOOSELY ORGANIZED WITH THIS
ACTIVITY.  STILL, IT INDICATES LOCAL AMOUNTS OF 3-4" VAGUELY
NEARBY, WHICH WOULD CAUSE ISSUES IN URBAN AREAS/TOWNS WITHIN THE
REGION AND COULD FALL QUICKLY.  THE AVAILABLE MOISTURE SUGGESTS
THAT HOURLY RAIN RATES COULD REACH 3" WITHIN CONVECTIVE AREAS. 
HOWEVER, SOME OF THE REGION IS COMPOSED OF SWAMPS AND SLOW-MOVING
BAYOUS/SLOUGHS, WHICH CAN HANDLE HEAVY RAINFALL.  FLASH FLOODING
IS CONSIDERED POSSIBLE, PARTICULARLY WITHIN URBAN AREAS.

ROTH

ATTN...WFO...BMX...MOB...TAE...

ATTN...RFC...SERFC...

LAT...LON   31788600 31638491 31098489 30358509 29918542 
            30018567 30148590 30358660 30298700 30328746 
            30788736 31468712 31668690